Technical Abstract:
Justification of Study
Outbreaks of gastrointestinal illness from exposure to pathogens in recreational and municipal drinking waters often focus public attention on animal agriculture as a potential source of contaminates in surface and ground water. Recent observations by researchers in Georgia have indicated that ponds with stream inflows and outflows reduce the concentration of fecal bacteria in downstream surface water. A systematic study, however, is needed to substantiate these observations and evaluate the utility of ponds for reducing concentrations of fecal bacteria in watersheds.
Objective
We have designed research to test the hypothesis that ponds downstream from a source of fecal pollution can reduce the load of fecal indicator bacteria (E. coli and fecal enterococci) and pathogen contamination (Salmonella and E. coli 0157:H7) of surface waters below ponds. Specific objectives are 1. determine the spatial and temporal distribution of fecal indicator bacteria and pathogens in inflow, within pond, and in outflow, 2. determine load reduction efficiency during base and storm flow, and 3. determine relationships between fecal indicator bacteria and the pathogens.
Progress to Date
Results of 31 months of baseflow sampling from Bishop Pond in Georgia’s Southern Piedmont indicated a recurring pattern in which concentrations of E. coli and fecal enterococci in pond outflow were significantly reduced compared to pond inflow concentrations. This pattern of inflow/outflow concentrations of fecal indicator bacteria was also observed for two storm events at Bishop Pond. Inflow/outflow concentrations of E. coli 0157:H7 and Salmonella, however, did not follow the pattern of the fecal indicator bacteria. Because of drought conditions and lack of pond inflow and outflow such recurring patterns have not been observed for the two ponds in Georgia’s Southern Plain. With modified MPN methods dilute concentrations of both E. coli 0157:H7 and Salmonella were determined for several samples assayed from the two Southern Plain ponds. Two in situ survival experiments with sentinel chambers were completed at Bishop Pond. Results of these experiments indicated that E. coli 0157:H7 survived twice as long as generic E. coli and more than 6 times longer than fecal enterococci. Unlike generic E. coli, E. coli 0157:H7 appeared to be immune to microbial predation.
Impact and Outputs
Jenkins, M.B., D.M. Endale, and D.S. Fisher. 2008. Most probable number methodology for quantifying dilute concentrations and fluxes of Salmonella in surface waters. J. Appl. Microbiol. 104(6):1562-1568.
Jenkins, M.B., D.M. Endale, and D.S. Fisher. 200-. Most probable number methodology for quantifying dilute concentrations and fluxes of Escherichia coli O157:H7 in surface waters. J. Appl. Microbiol. (In press).